Vehicles are refueled by dispensing fuel from underground storage tanks into a vehicle fuel tank. A small but measurable amount of fuel vapor is emitted during refueling due to the displacement of vapors from the vehicle fuel tank and release of vapors due to turbulently dispensing fuel from the refilling nozzle into the fuel filler pipe. The amount of vapor emissions varies in part based upon the temperature of the fuel dispensed into the fuel tank and the temperature of fuel within the fuel tank. The temperature of fuel obtained from underground storage tanks is approximately 65.degree.-70.degree. F. Temperature of fuel within the fuel tank which is heated by warm air flowing underneath the car from the engine and vehicle cooling systems can exceed 80.degree. F. The warmer the fuel the more volatile and greater the quantity of vapor emissions can be expected during refueling.
Prior art attempts to overcome the problem of vapor recovery during refueling have generally focused on adaptation of fuel dispensing nozzles to include vapor recovery systems. In particular, U.S. Pat. No. 3,921,412 to Heath et al. discloses a refrigeration system for fuel dispensing nozzles which condense vapors emitted from a fuel filler pipe.
Recently, environmental regulations requiring reduction of emissions during refueling have been promulgated that will necessitate on-board systems for reducing vapor emission during refueling. One approach to meeting these requirements is to provide a carbon canister at the inlet of the fuel filler pipe as proposed in U.S. Pat. No. 4,572,394 to Tanahashi et al. Carbon canister systems are expensive and add weight to vehicles which is counterproductive to fuel efficiency requirements.
The above problems have failed to provide a solution as proposed in the present invention as summarized below.